Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 241408
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
400 AM HST Fri Nov 24 2017

.SYNOPSIS...
High pressure far north of the state will keep breezy to windy
trades over the islands through the holiday weekend into early next
week. Passing showers will favor windward and mauka areas, with some
stray showers reaching lee areas of the smaller islands under the
robust trades. A wet trade wind weather pattern is expected to
develop on Sunday and continue through early next week, as deep
tropical moisture spread to the area from the southeast. The
wettest conditions are expected over the eastern end of the island
chain.

&&

.DISCUSSION...
Breezy to windy trades continue over the island chain early this
morning, as a strong surface high pressure moves to far north of the
area. Low clouds embedded in the wind flow are passing over the
islands at times, bring showers mainly to the windward and mountain
areas. Some clouds and showers have also reached the lee areas of
the smaller islands due to the rather robust trades. In fact, winds
remain strong enough to warrant the extension of the Wind Advisory
for portions of Maui county and the Big Island through early
Saturday. Rainfall amounts reported are modest at best, as much of
the passing showers are moving quite swiftly. Latest satellite
imagery revealed more low clouds are present upstream of the
islands early this morning. Some high clouds are clipping the
southern end of the Big Island, and may keep skies a little more
cloudy for that area today.

The breezy to windy trades will continue through the holiday
weekend, as the strong high pressure far north will drop south but
weaken somewhat over the weekend. It will be replaced by another
high from the far northwest by early next week. Regardless, expect
pressure gradient to stay rather tight across the islands through
the next few days, especially Saturday and Sunday. Therefore, shall
not be surprised to see the current Wind Advisory to be extended
again, with even a larger areal coverage possible. In all, trade
wind weather will prevail through the holiday weekend, with passing
low clouds and showers affecting mainly windward and mountain areas.

Wet trade wind weather is expected next week, as the latest forecast
models still indicated tropical moisture from the southeast will
spread northwest, reaching the eastern end of the island chain on
Sunday. Airmass over the islands may also become a little more
unstable as the models hinted some weak mid-level features may pass
over the area by the early portion of next week. Looks like the bulk
of the moisture will linger over the eastern islands, thus Maui
County and the Big Island should see the most clouds and showers.
Meanwhile, the rest of the islands will have their share as well,
though probably not as much as the eastern islands.

Furthermore, the tropical moisture is expected to be deep enough to
reach the Big Island summits. Combining with the cold temperatures
aloft, winter weather may affect those summits as early as Sunday
and may continue through early part of next week. Although it`s too
early to determine how much snow the summit areas will see, warning
level amounts are quite possible. A Winter Storm Watch will likely
be posted in the coming days.

&&

.AVIATION...
Trade winds will remain strong through the weekend. AIRMET Tango
remains in effect for moderate low level turbulence over and
downwind of the higher terrain due to the strong winds. AIRMET Tango
is also in effect for strong surface wind speeds for Lanai and
portions of the Big Island. Both of these AIRMETs are expected to
remain in effect through today.

Cloud and showers will be most prevalent over windward areas, and
AIRMET Sierra for mountain obscuration remains in effect for
windward parts of Big Island. While some of the showers will reach
leeward areas at times due to the strong trades, expect VFR
conditions to prevail there.

&&

.MARINE...
A High Surf Warning remains in effect through this evening for the
north and east facing shores of all islands due to a very large
north swell plus high wind waves due to strong to near-gale force
northeast trade winds. Wave heights continue running higher than
forecast by the Wave Watch III model. The longer-period swell has
peaked, but the shorter-period waves have continued to increase, so
combined seas have not dropped much. There will be large waves
breaking in north facing harbor entrances and possibly surges in
those harbors, so a Marine Weather Statement remains in effect. The
swell will slowly subside through tomorrow. A new north swell
starting on Sunday will peak on Monday and subside through Tuesday.
Surf from this swell may reach advisory levels. A northwest swell is
expected next Wednesday.

A Small Craft Advisory (SCA) is in effect through tomorrow morning
for Big Island Windward waters and through Sunday evening for strong
to near-gale force northeast trade winds and large seas due to a
combination of large wind waves and the large north swell. Trade
winds are expected to remain strong through the first half of next
week, and a new north swell will keep the seas high, so the SCA will
likely be extended further.

See the latest Oahu Surf Discussion for additional details on surf
and swell.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 PM HST this evening for Niihau-Kauai
Windward-Kauai Leeward-Oahu North Shore-Oahu Koolau-Olomana-
Molokai-Maui Windward West-Maui Leeward West-Maui Central Valley-
Windward Haleakala-Big Island North and East.

Wind Advisory until 6 AM HST Saturday for Lanai-Big Island North
and East-Kohala.

Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

Small Craft Advisory until 6 AM HST Saturday for Big Island
Windward Waters.

&&

$$

DISCUSSION...Hui
AVIATION...Jacobson
MARINE...Donaldson


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